Dependent Absorption and Extinction of Radiation by Small Particles

This study presents an analytical model to evaluate the dependent absorption and extinction characteristics of dense particulate systems. Simple expressions are obtained by considering statistical averages based on the random character of the particulate medium. Departure from the assumption of independent scattering and absorption of radiation originates from two mechanisms: perturbation of the internal field of each particle by the presence of other particles, and coherent addition (i. e., taking into account the constructive/destructive interference) of the far-field scattered radiation. Dependent scattering has been previously studied analytically by considering the second mechanism only. Dependent absorption, which is due to the former, has not been considered in the literature even though absorption is more important than scattering in the extinction of radiation by small (Rayleigh) absorbing particles.